C: (type) cast inside a constant expression (array dimension)

• Type: bug — Track C (const-expr evaluator)
• Opened: 2026-06-26
• Found-by: lua ltable unsigned int nums[MAXABITS + 1], where MAXABITS = cast_int(sizeof(int) * CHAR_BIT - 1) = ((int)(...)).

Symptom

int a[(int)4]; -> parse error ("Expected ], got ("); enum { X = (int)7 } also mis-folds. CEvalConstPrimary (cparser.inc) treats ( only as grouping, never as a cast, so the cast type tokens are not skipped and the operand is not folded.

Attempt + open puzzle (read before retrying)

Added a cast branch to CEvalConstPrimary's tkLParen case: if IsCTypeTok after (, skip the type tokens to the matching ) then fold the operand with CEvalConstPrimary. The grouping path (2+3) stayed correct, but the ARRAY dimension still failed: a debug at the local-array dim (arrLen := CEvalConstExpr) showed CurTok = tkLParen (74) BEFORE the call yet arrLen = 0 and CurTok = 2 AFTER — i.e. CEvalConstExpr returned without folding the cast even though the same CEvalConstPrimary edit folded an enum value. Two different behaviours from the one function = something context-dependent (token-kind numbering? a second const path? IsCTypeTok state?). REVERTED rather than ship an inconsistent/partial const-eval.

Fix direction

Pin why the local-array-dim CEvalConstExpr path and the enum path diverge (add the debug back: print Ord(CurTok.Kind) + CurTok.SVal at entry of CEvalConstPrimary and at the local-array dim; compare the two call sites). Then handle (type)expr once in CEvalConstPrimary. Note a SEPARATE token-based struct-field array-dim evaluator at cparser.inc ~2591 only reads tkInteger and must also learn casts//. Common: lua MAXABITS / cast_int / luaM_limitN array sizes.

Resolution

• 2026-06-26 — FIXED. Root was the bare-funcname=Result landmine: the new cast branch wrote Result := CEvalConstPrimary WITHOUT parens, so inside CEvalConstPrimary that read the functions own Result (0) instead of recursing, leaving the operand unfolded. CEvalConstPrimary()` with parens fixes it. Fixture cconst_cast_b39.c (=42); lua ltable now parses.